Trichoderma species are present in many ecosystems and some strains have the ability to reduce the severity of plant diseases by activating various defense pathways via specific biologically active signaling molecules. Hence we investigated the effects of low molecular weight volatile compounds of Trichoderma asperellum IsmT5 on Arabidopsis thaliana. During co-cultivation of T. asperellum IsmT5 without physical contact to A. thaliana we observed smaller but vital and robust plants. The exposed plants exhibit increased trichome numbers, accumulation of defense-related compounds such as H2O2, anthocyanin, camalexin, and increased expression of defense-related genes. We conclude that A. thaliana perceives the Trichoderma volatiles as stress compounds and subsequently initiates multilayered adaptations including activation of signaling cascades to withstand this environmental influence. The prominent headspace volatile of T. asperellum IsmT5 was identified to be 6-pentyl-α-pyrone (6PP), which was solely applied to A. thaliana to verify the growth and defense reactions. Most noticeable is that A. thaliana preexposed to 6PP showed significantly reduced symptoms when challenged with Botrytis cinerea and Alternaria brassicicola, indicating that defense-activated plants subsequently became more resistant to pathogen attack. Together, these results support that products that are based on Trichoderma volatiles have the potential being a useful biocontrol agent in agriculture.

Seaweeds are naturally rich with biological active metabolites that could be promising to be used in the biological control. The present study was conducted to evaluate the antifungal potentiality of metabolites extracted from Ulva fasciata, Ulva lactuca and Cladophora sericea; against Macrophomina phaseolina (Tassi) Goid. and Fusarium oxysporum Schltdl. Four organic solvents hexane, chloroform, acetone and methanol were used for extraction of seaweeds metabolites to assay their biological efficiency on mycelium growth reduction of two candidate soil borne fungal pathogens on potato dextrose agar medium. The highest percentage of F. oxysporum and M. phaseolina growth reduction was observed by acetone extract of U. fasciata and methanol extract of C. sericea. The highest inhibition against M. phaseolina reached up to 28.97% by U. fasciata acetone extract and 24.77% by C. sericea methanol extract. The highest percentage of mycelial growth inhibition of F. oxysporum was observed by U. fasciata acetone extract (23.58%) and C. sericea methanol extract (17.01%). Analysis of acetone extract of U. fasciata by gas chromatography mass spectrophotometer GC/MS revealed the presence of some organic compounds with antifungal properties such as Phenol, 2,2'-methylenebis[6-(1,1-dimethylethyl)-4-methyl-, Di-n-octyl phthalate, 1,2-Benzenedicarboxylic acid, diisodecyl ester, Didecyl phthalate, Phthalic acid, bis (7-methyloctyl) ester, gamma Sitosterol, Cholest-5-en-3-ol, 24-propylidene-, (3. beta.) and Cyclononasiloxane, octadecamethyl-. The results suggest that the studied algal species can be used as potential bio-agent source in biological control of soil borne phytopathogenic fungi.

No abstract

Egyptian Journal of Botany http://ejbo.journals.ekb.eg/ 2050 T HE APPLICATION of cyanobacteria metabolites in agriculture is considered a promising alternative to chemical fungicide because they are rich in many bioactive metabolites. Antifungal potentiality of Desertifilum tharense PS 11 extracts with different solvents was tested in vitro against Fusarium oxysporum f. sp. lycopersici. The D. tharense PS 11 methanol extract showed the highest antifungal activity against F. oxysporum (19.11%). Then, it was analyzed by GC-MS and LC-ESI-MS to identify and quantify its bioactive compounds. GC-MS and LC-ESI-MS analysis of D. tharense methanol extract investigate that the extract was rich in several metabolites such as phenols, alkanes amino acids, peptides, flavonoids, fatty acids and phthalic acid derivatives. After that, pot experiment was performed to test the efficiency of D. tharense PS11 methanol extract in the control of tomato vascular wilt disease caused by F. oxysporum f. sp. lycopersici and growth promotion activity. Correspondingly, the results indicate a 50% reduction in disease incidence. Furthermore, D. tharense methanol extract exhibited a significant effect on plant growth and tomato yield. Therefore, this study clearly demonstrated that methanol extract from D. tharense PS 11 is a promising biochemical control agent against F. oxysporum f. sp. lycopersici and can enhance tomato growth.

A TOTAL of twenty Trichoderma isolates belonging to seven species were isolated from several locations at Port Said Governorate. Physiological characteristics of these isolates and their antagonistic effect against Sclerotinia sclerotiorum, the causative agent of white mold of Phaseolus vulgaris were evaluated. Trichoderma polysporum 2 showed the highest activity of total cellulase reached up to 2.95 filter paper unit ml-1. T. harzianum 2 had the highest endoglucanase activity (5.47 IU ml-1), whereas T. polysporum 1 had the highest chitinase activity (1.01 IU ml-1). Siderophores production was assayed using FeCl 3 , tetrazolium, Arnow's and spectrophotometric tests. Most of the isolates were able to produce hydroxamate and carboxylate types of siderophores. The ability of Trichoderma to produce indole acetic acid (IAA) and gibberellic acid (GA 3) were also investigated. Trichoderma harzianum 2 showed the highest concentration of IAA in broth medium reached up to 13.19µg/ml, whereas T. polysporum 1 showed the highest concentration of GA 3 by 586.51µg/ml. The antagonistic potentialities of Trichoderma isolates against Sclerotinia sclerotiorum were tested in vitro by using dual culture, base to base assay and the crude liquid extract effect of the isolates. Percentages of inhibition of radial growth of the pathogen by T. polysporum 1 in dual culture and crude extract methods were 45.97% and 87.78%, respectively. Also, the volatiles of T. piluliferum 2 showed a reduction of the radial growth by 66.85%. So, some Trichoderma isolates collected from Port Said soil showed high biocontrol activity against S. sclerotiorum.